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Melanocortin-4 receptor activation inhibits c-Jun N-terminal kinase activity and promotes insulin signaling

Biaoxin Chai1, Ji-Yao Li, Weizhen Zhang

  • 1Department of Surgery, University of Michigan, 2101 Taubman Center, Ann Arbor, MI 48109-0346, USA.

Peptides
|May 26, 2009
PubMed

Insights

The melanocortin system, involving melanocortin receptor type 4 (MC4R), influences insulin signaling by affecting c-Jun N-terminal kinase (JNK). This study reveals novel interactions between the melanocortin system and insulin signaling pathways.

Area of Science:

  • Endocrinology
  • Neuroscience
  • Cell Biology

Background:

  • The melanocortin system is vital for regulating energy balance.
  • Melanocortin receptor type 4 (MC4R) plays a role in modulating insulin signaling.
  • Previous research suggests a link between melanocortins and metabolic regulation.

Purpose of the Study:

  • To investigate the interaction between the melanocortin system and insulin signaling.
  • To elucidate the role of melanocortins in regulating key components of insulin signaling pathways, such as JNK and AKT.
  • To determine the effect of melanocortin agonists on insulin-stimulated glucose uptake.

Main Methods:

  • Utilized HEK293 cells stably expressing human MC4R to assess JNK activity.
  • Employed Western blotting to analyze the phosphorylation status of IRS-1 and AKT.
  • Investigated cellular responses in hypothalamic GT1-1 cells and in vivo rat hypothalamus models.

Main Results:

  • NDP-MSH, a melanocortin agonist, dose-dependently inhibited JNK activity and IRS-1(ser307) phosphorylation in MC4R-expressing cells.
  • These inhibitory effects were reversed by a melanocortin receptor antagonist.
  • NDP-MSH enhanced insulin-stimulated AKT phosphorylation in vitro and in vivo, and increased glucose uptake in hypothalamic cells.

Conclusions:

  • The melanocortinergic system directly interacts with insulin signaling pathways.
  • Melanocortins modulate insulin signaling through novel effects on JNK activity.
  • These findings highlight a potential therapeutic target for metabolic disorders.

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